Purchase resale weeks for good trading resorts like Grand Chateau, Grande Vista, Desert Springs. Make sure they are lockoffs. Reserve your weeks that have the highest trading power in Interval, then lock them off and deposit into interval and find the best weeks you can via trading. You can also grab some getaways in December for Florida and other warm places.
You're probably not going to get Palm Beaches or Aruba in February, but using that strategy plus supplementing it with DC points I'm spending 19 days in November at Barony Beach Club in Hilton Head, then 19 days in Orlando in December (haven't decided which resort yet), Christmas and New Year's weeks in Orlando at Grande Vista, then about a month in Hilton Head again before we come home. For the time being we're going to come back home Feb/Mar (I like March in Maryland), but it wouldn't be expensive to stretch out Hilton Head into those time frames as long as you don't need Oceanfront or South Florida.
Using points only to do all that would be well over 10K points. I think I used about 3K plus two Accommodation Certificates from II and one week deposited, locked off, and traded back into two weeks.
The California desert resorts are a lot like Hilton Head as far as availability goes (plenty in Fall and into January, nada in March/April unless you have a REALLY good trader) - just too far for us to drive while I'm still employed (I work from home so can bring my work stuff wherever I go).
It's quite a game and I spent a few hours playing around on Interval and asking a ton of questions on TUG, and I'm still a total newbie at this so I would imagine there are even better ways to accomplish "wintering" without having to buy 15,000 DC points and paying the $8K/year in maintenance fees.